Emacs is the only app you'll ever need once you've mastered it.

I discovered warpinator recently, useful for transferring files to my android phone.

When I finally learned about Pocket just a few years ago it surprised me greatly that I didn't know about it before and now I use it daily:

https://en.wikipedia.org/wiki/Pocket_%28service%29

https://www.byobu.org/ can eschew both screen and tmux Mosh (the mobile SSH client, not linking here) if installing it on the remote server is an option

K9S, it is a TUI kubernetes manager that really integrates well into my workflow.

• Obsidian - great markdown-based note app
• NewsFlash - fast and elegant RSS news reader
• Bottles - program to run Windows apps and managing them easily
• BreakTimer - a life-saver for me; it allows you to set a break after given amount of time
• LibreWolf - privacy-focused fork of Firefox

There are a lot of awesome programs on Linux, I recommend browsing Flathub to find them

Htop vim and ncdu to name a few terminal apps.